NO332082B1 - Method and apparatus for pyrolysis and gasification and organic substances or mixtures of substances - Google Patents

Abstract

The present invention relates to a process for pyrolysis and gasification of organic substances or mixtures of organic substances. The organics are introduced into a drying and pyrolysis reactor (1) in which they are contacted with the fluidized bed material (35) to the combustion fluidized bed (3) or in which they are contacted with the fluidized bed material (35) and the reactor wall of the combustion fluidized bed (3) whereby a drying and pyrolysis takes place. The solid carbonaceous residue, optionally with portions of the vapor and of the pyrolysis gases, and the fluidized bed material is fed back into the combustion fluidized bed (3) into which the carbonaceous residue of organics is burnt to ash, the fluidized bed material is watered, and is again fed. in the pyrolysis reactor (1). Steam from the drying and pyrolysis gases (13) are subsequently treated with condensable substances in a further reaction zone (2) so that a product gas (23) with a high combustion value is available. The drying and pyrolysis are carried out in at least one or more pyrolysis reactors (1). The combustion fluidized bed (3) in which the pyrolysis residues are burnt to ashes is operated as a stationary fluidized bed. The pyrolysis gases (13) are fed into an indirect heat exchanger. The heating fumes (37), optionally with the fluidized bed material of the combustion fluidized bed (3), are contacted with the indirect heat exchanger (2) so that their heat content is used for reaction of the pyrolysis gases (13) with the reaction agent (21).

Description

The present invention relates to a method for pyrolysis and gasification of organic substances or mixtures of organic substances, as well as a device for carrying out a method.

A number of methods are known for the treatment and use of organic substances and mixtures of organic substances by, for example, gasification and pyrolysis. The methods differ according to the oxidizing or reducing gas used and according to the type of contact between the solid and the gas. In the case of solid or gas flow, a distinction is made between i.a. a circulating fluidized bed gasifier, an entrained bed gasifier, a rotating combustion chamber gasifier and a moving bed gasifier with counter-flow gas flow, co-flow gas flow or cross-flow gas flow. The majority of known gasification methods are not suitable for smaller, decentralized systems due to the high equipment input. Smaller, decentralized systems are advisable especially when biomass is used as application material.

The operational behavior of gasification processes according to the principles of the circulating fluidized bed is highly dependent on respective particle size in the fluidized bed consisting of the application material to be gasified and also the circulating inert material. Corresponding requirements form the basis for the particle size of the application material. There are extremely high requirements for the preparation of the fuel in the case of entrained bed gasification, which only allows the use of powdered fuel particles.

Further significant disadvantages of the known gasification methods are that the subsequent process steps of drying, degassing, gasification and incineration to ash of the application material proceed in zones which are directly next to each other and which flow into each other. As a result, the individual zones inside a reactor are undefined, and the degassing, gasification, and combustion to ash may progress incompletely at points. In further known methods, attempts have been made to eliminate these disadvantages by separating the individual process steps for the fuel with degassing, gasification and combustion to ash.

DE 197 20 331 Al proposes a method and a device for the gasification or burning to ash of dry or moist, fine-particle or fragmentary biomass and of waste in which the hot walls of a combustion chamber and the narrowing of hot waste gas from the combustion chamber into in a degassing furnace, biological raw materials degas in this, whereby coke and pyrolysis gas are produced, where the coke arrives in the globe of the gasification reactor after passing the coarser (tailor), as the pyrolysis gas burns in the combustion chamber of the gasification reactor under the supply of a limited amount of air, and the waste gas which produced then flows through the bed to the gasification reactor in which an oxidation of the carbon to CO takes place with a simultaneous reaction of waste gas (CO2) and steam

(H2O) to a flammable lean gas (CO, H2). Due to the fact that the pyrolysis is carried out due to the heating due to the contact with hot combustion waste gases and further that a partial combustion of the pyrolysis gas is carried out, only a product gas with a low calorific value can be produced with the method proposed in DE 197 20 331 Al. When fuels with a high content of volatile components and a low pyrolysis coke yield are used, there is a risk of a sufficient formation of the globe for the gasification reactor consisting of pyrolysis coke, whereby the oxidation of carbon to CO with a simultaneous reduction of waste gas and steam to combustible lean gas progresses insufficiently to the cost of product gas calorific values.

A method is additionally known from U.S. Pat. 4,568,362 for gasification of organic substances and mixtures of organic substances in which the organic substances are led into a pyrolysis reactor in which the organic substances will come into contact with a heat transfer medium, whereby a rapid pyrolysis takes place which converts the organic substances to pyrolysis products consisting of pyrolysis gases with condensable substances and a solid carbonaceous residue, and the required heating energy for the pyrolysis is produced by burning the solid carbonaceous residue in a combustion reactor and in a second reaction zone of the pyrolysis reactor, which pyrolysis gases containing tar are subjected to such cracking reactions and reactions with steam so that a product gas with a high calorific value is obtained. In these methods, both the pyrolysis and the burning to ash of the solid carbonaceous residue take place in a fluidized bed. A reaction zone for the pyrolysis gases containing tar is provided in the upper part of the pyrolysis fluidized bed. The operation of the fluidized beds requires a high effort, and control of the reactions of the pyrolysis gases in the reaction zone is hardly possible.

The German patent application 197 77 693.0 with older priority, and not previously published, on the basis of which German patent DE 197 55 693 Cl has been granted a patent, describes a method for the gasification of organic substances and mixtures of organic substances.

Regarding prior art, reference should also be made to WO 9931197 A1 and to US 4244779 A.

It is the underlying purpose of the present invention to provide a method which is easy to carry out for pyrolysis and gasification of organic substances or mixtures of organic substances, as well as a device for generating a gas with a high calorific value.

These objects are solved by means of the features in claims 1 and 11. Advantageous embodiments and further developments of the invention follow when using the features set forth in the dependent claims.

In a method for pyrolysis and gasification of organic substances or mixtures of organic substances, this purpose is solved in accordance with the invention in that the pyrolysis is carried out in a moving bed reactor or a rotating reactor, that a gasification agent, for example steam and/or oxygen, is optionally added to the pyrolysis gases and that they are led into a reaction zone in which the pyrolysis gases react with the reaction agent. The solid carbonaceous residue, and optionally a portion of the pyrolysis gas, is directed to a fluidized bed combustion reactor alone or together with the fluidized bed material and burned to ash there. The fluidized bed material is heated there. The combustion waste gases and the fluidized bed material are brought into contact with the reaction zone so that their thermal content can be used for reaction between the pyrolysis gases and the gasifier. Fluidized bed material taken from the fluidized bed combustion reactor, and consisting of ash, unburnt coke and, optionally, additionally supplied refractory fluidized bed material, is returned to the pyrolysis reactor as a heat transfer medium, where heat transfer to the application material for carrying out the pyrolysis takes place by contact with the fluidized bed material and optionally additionally through it heat the wall of the fluidized bed combustion reactor.

The hot fluidized bed material supplied to the pyrolysis reactor from the combustion fluidized bed causes rapid drying and pyrolysis of the application material upon contact. A shaft furnace is suitable as a reactor, where the mixture of the application material and the fluidized bed material travels from the top to the bottom through the shaft furnace. To ensure solids transport through the shaft furnace, fixed equipment, transport screws or agitators can be provided in accordance with the prior art. The pyrolysis reactor can, for example, be designed as a rotating reactor, whereby a good mixture of the application material and the hot fluidized bed material is achieved, and that at the same time solids transport is achieved. The steam that escaped from the application material during drying and the pyrolysis gases leave the pyrolysis reactor and enter a further reaction zone. The mixture of the remaining solid carbonaceous pyrolysis residue and the fluidized bed material is transported together into the combustion fluidized bed, where conventional components such as conveyor screws or star wheels with inclined tubes carrying in are able to be used. A screw is preferred in the device according to the present invention.

Due to the fact that the pyrolysis is preferably carried out in a shaft furnace, the supply of a fluidizing medium required for a pyrolysis fluidized bed can be avoided. In this way, the possibility exists to carry out the pyrolysis completely without adding gas, or unlike the pyrolysis fluidized bed to which a minimum amount of gas must be added for fluidization, and adding any desired low amounts, for example of the product gas or of a gasifying agent such as steam, oxygen or air. In this way, the possibility of adding gas or a gasification agent to the pyrolysis reactor exists as a technical process adaptation to the respective application material. In the method according to the present invention, the pyrolysis is preferably carried out in the pyrolysis reactor in the absence of air and gas. Another advantage of carrying out the pyrolysis in a separate process step consists of the crushing effect that occurs during the pyrolysis and which allows the use of coarser fragmentary material than normally used in fluidized bed reactors due to the smoldering and degassing. Alternatively, there is the possibility of inserting a crushing device such as a roller crusher before the introduction device for the solid carbonaceous pyrolysis residue and fluidized bed material into the combustion fluidized bed, whereby the requirements for the particle sizes of the application material can be further reduced. Here, the energy used for crushing pyrolysis coke is substantially less than that for crushing, for example, biomass, such as wood.

The carbonaceous solid pyrolysis residue is burned to ash with air in the fluidized bed, and thus becomes fluidized bed material itself as ash and, due to the release of energy, further heated or reheats fluidized bed material that is already present. The combustion fluidized bed can be constructed and operated in accordance with the level of knowledge of fluidized bed technology. A gradual supply of air can be advantageous with regard to the emissions from the combustion fluidized bed. The combustion reactor is designed as a stationary fluidized bed, which means that the gas quantity of the fluidized medium must be sufficient, on the one hand, to exceed the minimum fluidization rate of the solid, and must, on the other hand, exceed the yield rate. From a fluidized bed height of approx. 2.5 meters to 3 meters, a fixed device is required to prevent the formation of a pulsating fluidized bed and the accompanying pressure pulsations. The fluidized bed material heated by the combustion procedure is finally fed back into the pyrolysis reactor. The fluidized bed material consists of the ash remaining from the combustion to ash of the solid carbonaceous residue. If an incomplete combustion of the pyrolysis coke inside the combustion fluidized bed takes place, the fluidized bed material which is passed in the circuit as the heat transfer medium consists of the ash of the application material and of unburned carbonaceous pyrolysis residue. When the solid carbonaceous residues of organic substances and mixtures of organic substances are, as a rule, rapidly transformed in the combustion fluidized bed and can partly only have smaller parts of the material that cannot be gasified or burned to ash, it is optionally necessary to add additional material to form a fluidized bed. The additional material does not need to be added if the application materials have large amounts of the material that cannot be gasified or burned to ash, which is suitable for building up a fluidized bed. All refractory materials such as sand with a grain diameter of less than 1.5 mm are suitable as feed material, and which serve to form a fluidized bed. The removal of the hot fluidized bed material and the transport into the pyrolysis reactor is preferably effected by means of one or more overflows which are provided in the reactor wall or which project through the reactor wall and into the fluidized bed. This method has the advantage that in addition to the transfer of hot fluidized bed material into the pyrolysis reactor, the fluidized bed height of the combustion fluidized bed can be adjusted in a simple way. The removal of fluidized bed material can also be carried out using other known conveyors, such as a conveyor screw. However, in this case the technical method performance is higher.

The present invention is based on the basic idea of structuring the method in process steps that are easy to perform. The individual process steps and their interaction can therefore be ideally designed by taking into account the particular characteristics of the application material and with regard to the intended product gas quality to be achieved.

Further advantages of the present invention are shown in the drawings described below, in which preferred embodiments of the invention are shown by way of examples. In the drawings, Figure 1 shows the mass flows and energy flows to the pyrolysis step, to the reaction zone and to the combustion fluidized bed according to the method according to the invention; Figure 2 an embodiment of the method according to the invention in a

schematic representation; and

Figure 3 an embodiment of the device according to the present invention in a schematic representation.

It can be seen from figure 1 that the application material 10 and the fluidized bed material 35 are supplied as the heat transfer medium into the pyrolysis step 1. The heat flow which

transported with the fluidized bed material 35 results from the temperature of the combustion fluidized bed, from the state and mass flow of the fluidized bed material 35 and from the application material stream 10 and from the desired pyrolysis temperature. In addition, a gasifier 11 is added, and a heat stream 34 is transferred from the combustion fluidized bed 33. From the pyrolysis stage 1, pyrolysis gas 13 exits, which is led into the reaction zone 2, pyrolysis gas 15, which is led into the combustion reactor (to the combustion fluidized bed 33) , a mixture of the fluidized bed material and solid carbonaceous pyrolysis residue 14 and a heat loss stream 12.

The mixture of fluidized bed material and solid carbonaceous pyrolysis residue 14 is led into the combustion fluidized bed 3 together with pyrolysis gas 15 and air 31. The fluidized bed material 35 heated by the combustion to ash is led back into the pyrolysis reactor 1. The also hot exhaust gas 37 exits the combustion fluidized bed 3. Part of the heat 36 contained in the exhaust gas is transferred to the reaction zone 2. A heat loss stream 33 and fluidized bed material 32 which must be removed in order to regulate the total solids content (household) in stationary operation also leave the combustion reactor 3.

The pyrolysis gas 13 supplied to the reaction zone 2 is transferred together with the gasifier 21 into the product gas 23 by means of the supplied heat 36 in the presence of a catalyst. The product gas 23 and the heat loss stream 22 finally exit the reaction zone 2.

Embodiment

In the following example, the preferred method and device according to the present invention is described. The preferred method according to Figure 2, and the preferred device according to Figure 3 serve for pyrolysis and gasification of 900 kg at pr. hour. The wood used as an example essentially consists of 52.3 weight percent carbon, 5.9 weight percent hydrogen and 41.8 weight percent oxygen, in each case with respect to the fuel substance free of water and ash, and additionally has an ash proportion of 0, 51 percent by weight in relation to the raw material used. The calorific value of the wood amounts to Hu = 17.2 Mj/kg with regard to the state free of water, and the thermal gasifier effect thus amounts to 3.92 MW.

In the preferred embodiment described in Figure 2 for the method for wood gasification, wood 10 is subjected to crushing and/or drying in a preparation step 4 depending on the condition of the application material before it is led into the pyrolysis step 1. The wood has a water content of 8, 9 percent by weight after preparation step 4.

The pyrolysis is carried out at a temperature of 580 °C. The fluidized bed material 35 introduced into the pyrolysis reactor 1 has a temperature of 900 °C, so that the 4.1-fold amount of fluidized bed material, i.e. 3.7 tonnes per hour, must be supplied and circulated to heat the application material to the pyrolysis temperature of 580 °C. During pyrolysis of the wood, 20.3 percent by weight (in relation to the fuel, raw) is finally left as the solid pyrolysis residue, which has a burning value of Hu = 30 MJ/kg. The residual products from the drying and pyrolysis leave the pyrolysis reactor 1 as the gas 13 and enter the reaction zone 2. The mixture of solid pyrolysis residue and fluidized bed material 14 is supplied to the combustion fluidized bed and burned there with air 31. The enthalpy flow supplied to the combustion fluidized bed with the solid pyrolysis residue of the wood amounts to to 1.52 MW. In the present example, a power surplus is again connected to the flue gas stream 37 in the combustion fluidized bed material 3 after removal of the heat loss 33, of the removed fluidized bed material 32, of the fluidized bed material 35 and of the energy quantity 36 transferred to the reaction zone 2. For this reason, a superheated steam stream formed with a water stream 70 subjected to treatment 7 while taking into account firing efficiency in the heat transfer element 8. If the steam stream 21, which is supplied to the reaction zone 2, is taken from the superheated steam stream formed in 8, a superheated steam stream 71 is left with an effect of 0.45 MW which is pressure relieved via a turbine 9.

During the supply of the reaction agent of steam 21, the pyrolysis gases 13 are led into the reaction zone 2 consisting of a heat transfer element which is matched with a catalyst to improve tar cracking. The energy required for the reaction between the pyrolysis gas 13 and the steam 21 is radiated to the heat transfer element 2 via the hot flue gas stream 36 from the combustion fluidized bed 3, where the reaction

takes place at 850 °C to 900 °C depending on the operational control of the combustion fluidized bed 3. Air or oxygen can also be mixed into the gasifier by

gas 21 for a further increase in temperature by a partial combustion to ash of the pyrolysis gas. The product gas 23 that is obtained has a calorific value of 9.87 MJ per M<3>(Vn) and consists of the following gas components: 48.7 volume percent H^, 36.1 volume percent CO, 0.1 volume percent CH4, 6.1 volume percent CO2, and 9 volume percent H2O. The product gas 23 is in the subsequent dust preparation and quenched in a preparation step 5. The cold gas efficiency, in other words the chemical energy of the application material in relation to the chemical energy content of the product gas, amounts to 80.8%.

Figure 3 shows a preferred embodiment of the device according to the present invention for pyrolysis and degassing as an example sketch. The wood 10 is supplied to the pyrolysis reactor 1 via a gas impermeable conveying device, a star wheel in the example shown here. The drying and pyrolysis of the application material takes place by contact with the hot fluidized bed material 35 supplied by an overflow from the combustion fluidized bed 3. The produced pyrolysis gas 13 is led into the reaction zone 2 while steam 21 is supplied, which reaction zone in the example here is constructed as a tube heat transfer element . After the transformation of the pyrolysis gas 13 with the steam 21, the product gas 23 is cooled and purified in the preparation step 5. To avoid unwanted exchange of gases between the pyrolysis reactor 1 and the combustion fluidized bed 3, the fan for the product gas line and the fan for the flue gas line 60 must be adapted to each other. Due to the fact that the overflow from the combustion fluidized bed 3 to the pyrolysis reactor 1 is such that it is constantly filled with the fluidized bed material 35, then, in combination with said fans, the exchange of gas between both reactors is prevented in a simple way. A screw is preferably provided to transport the mixture of solid pyrolysis residue and circulating fluidized bed material 14 into the combustion fluidized bed 3. The screw must be designed so that the pressure loss through the screw passages filled with the material is greater than via the fluidized bed 3, so that the air 31 supplied to the combustion fluidized bed bed 3 does not flow in the circuit

through the pyrolysis reactor 1. A steam stream 71, which is depressurized for example via a turbine 9, is produced from a water stream with the heat from the flue gas stream 37 via a heat transfer element 8. Part of the steam stream 71 can be used as steam 21 for the reaction zone 2. The exhaust gas 60 is added to a flue gas purification 6.

Referral designation list:

1 pyrolysis reactor

10 application material

11 reagent

12 heat loss

13 pyrolysis gas

14 mixture of solid pyrolysis residue and fluidized bed material

15 pyrolysis gas

2 reaction zone

21 gasifier

22 heat loss

23 product gas

3 firing

31 air

32 fluidized bed material

33 heat loss

34 heat flow

35 fluidized bed material

36 heat flow

37 combustion exhaust gas

4 pretreatment steps

5 gas purification

50 purified product gas

6 flue gas cleaning

60 exhaust gas

7 water treatment

70 water

71 steam

8 heat transfer element

9 turbine

Claims (15)

1. Process for pyrolysis and gasification of organic substances or mixtures of organic substances, characterized in that 1.1 the organic substances are introduced into a drying and pyrolysis reactor (1) in which the organic substances are brought into contact with fluidized material (35) of the combustion fluidized bed (3) or in which the organic substances are brought into contact with the fluidized bed material (35) and the reactor wall of the combustion fluidized bed (3) whereby a drying and pyrolysis takes place, in which the organic substances are converted into steam from the drying and into pyrolysis products ( 13), whereby the pyrolysis products consist of gases with condensable substances and solid carbonaceous residue; 1.2 the solid carbonaceous residue or the solid carbonaceous residue and parts of the steam and of the pyrolysis gases with condensable substances and the fluidized bed material are led back to the combustion fluidized bed (3) in which the carbonaceous residue of the organic substances is incinerated to ash (incinerated), the fluidized bed material is heated and is again led into the pyrolysis reactor (1); 1.3 the steam from the drying and the pyrolysis gases (13) are subsequently treated with condensable substances in a further reaction zone (2) so that a product gas (23) with a high calorific value is available; 1.4 the drying and pyrolysis are carried out in at least one or more pyrolysis reactors (i); 1.5 the drying and pyrolysis are preferably carried out in two or more pyrolysis reactors (1) consisting of two or more moving bed reactors or of two or more rotating reactors or of rotating reactors and moving bed reactors; 1.6 the combustion fluidized bed (3) in which the pyrolysis residues are burned to ash, is operated as a stationary fluidized bed; 1.7 no reaction agent, or optionally a gasification agent such as steam, oxygen or air or a mixture thereof is added to the pyrolysis gases (13); 1.8 the pyrolysis gases (13) are led into an indirect heat exchanger (2) in which they optionally react with the gasifier (21); 1.9 the combustion exhaust gases (37) or the combustion exhaust gases and the fluidized bed material of the combustion fluidized bed (3) are brought into contact with the indirect heat exchanger (2) so that their thermal content is used for the reaction between the pyrolysis gases (13) and the gasifier (21); 1.10 the fluidized bed material (3) consists only of the ash from the organic substances, or of the ash and unburned carbonaceous residues from the organic substances, or of the ash from the organic substances and of further fluidized material, or of the ash and unburned carbonaceous residues of the organic substances and of further fluidized material. 2. Method according to claim 1, characterized in that the pyrolysis is carried out at a temperature from 450 °C to 750 °C. 3. Method according to one of claims 1 or 2, characterized in that the product gas (23) is led back into the pyrolysis reactor (1). 4. Method according to any one of claims 1 to 3, characterized in that gasification agents (21) such as steam, oxygen or air or a mixture thereof are introduced to the pyrolysis reactor (1). 5. Method according to any one of claims 1 to 4, characterized in that the surface of the reactor wall of the combustion fluidized bed (3) has any closed geometric shape on the side of the pyrolysis reactor (1) and the combustion fluidized bed (3). 6. Method according to any one of claims 1 to 5, characterized in that the reactions between the pyrolysis gases (13) and the gasifier (21) are carried out at temperatures from 800 °C to 1050 °C. 7. Method according to any one of claims 1 to 6, characterized in that the reactions between the pyrolysis gases (13) and the gasifier (21) are carried out in the presence of a catalyst. 8. Method according to any one of claims 1 to 7, characterized in that the reactions (13) with the gasifier (21) are carried out in a fixed bed of catalyst material. 9. Method according to any one of claims 1 to 8, characterized in that the reactions between the pyrolysis gases (13) and the gasifier (21) are carried out in a fluidized bed of catalyst material. 10. Method according to any one of claims 1 to 9, characterized in that the reactions between the pyrolysis gases (13) and the gasifier (21) are supplied in the presence of a catalyst supplied to the pyrolysis gas (13) in the entrained stream. 11. Device for carrying out a method for pyrolysis and gasification of organic substances or mixtures of organic substances, in particular for carrying out a method according to one or more of claims 1 to 10, including a pyrolysis reactor (1), a fluidized bed firing (3) for the pyrolysis residue, a reaction zone (2) for the pyrolysis gases (13) and a fluidized bed material circulation between the combustion fluidized bed (3) and the pyrolysis reactor (1), characterized in that a shaft reactor or a rotary reactor with a sluice for application material and an inlet for the fluidized bed material from the combustion fluidized bed (3) is placed next to the combustion fluidized bed; in that the shaft reactor (l) has a transport device into the combustion fluidized bed at its lower end; in that the combustion fluidized bed (3) has an overflow to transfer the fluidized bed material into the shovel tractor (1); and in that the exhaust gases (37) from the pre-combustion fluidized bed (3) can be supplied to a heat transfer element (2) which is connected to the shaft reactor (1) for the pyrolysis gases (13). 12 Device according to claim 11, characterized in that the fluidized bed material can be removed from the combustion fluidized bed (3) at least in one point or in a plurality of points, and can be led into the pyrolysis sector. 13. Device according to one of claims 11 or 12, characterized in that the fluidized bed material can be removed from the combustion fluidized bed (3) at least in one point or in a plurality of points by means of one or more overflows and can be led into the pyrolysis reactor. 14. Device according to any one of claims 10 to 13, characterized in that refractory substances can be added to form a fluidized bed. 15. Device according to any one of claims 10 to 14, characterized in that the components of the application material which cannot be burned, and which cannot be gasified, can be used to form a fluidized bed.